In certain applications involving fluid transfer, it may be necessary to move fluid from a static fluid passage to a rotating fluid passage. For example, in neural transplantation, a cannula is inserted into a patient's brain and carefully and precisely rotated, often through several revolutions. An example of such a neural transplantation system is described in Canadian Patent No. 2,282,007 and U.S. Pat. No. 7,137,969.
For such applications in which fluid is to move from a static fluid passage to a rotating fluid passage, it is desirable to have a rotating union for sealingly coupling the static fluid passage to the rotating fluid passage.